Low Levels of Genetic Differentiation among Populations of the Coral-Inhabiting Snail Coralliophila violacea (Gastropoda: Coralliophilidae) in Regions of the Kuroshio and South China Sea

摘要

The coral-inhabiting snail, Coralliophila violacea, is a common species in Indo-Pacific coral reefs and usually aggregates on the surfaces of living massive Poritis corals. A previous study indicated a low genetic diversity (Nei' s genetic distance of< 0.003) for C. violacea of southern Taiwan (Lin 1992). Herein, we attempted to determine whether the low genetic differentiation extends to the South China Sea (SCS) by examining allozyme variations at 6 polymorphic loci. Snails were sampled from the Kuroshio region around Taiwan and the SCS which are 1500 km apart. The mean observed heterozygosity among the 7 populations varied from 0.155 to 0.293, with all indicating heterozygote deficiencies. We detected small but significant genetic differentiation among all populations (mean F_(ST)of 0.078); however, genetic distances (Nei's D) between populations were relatively low, ranging from 0 to 0.093. There was a positive trend, although insignificant, between the geographic distance and Nei's genetic distance (Mantel test, Z = 575.7, r = 0.66, p = 0.13). This pattern was confirmed by a UPGMA cluster analysis which showed that geographical-closed populations did not cluster together. The Kuroshio intrusion, high larval dispersal capability, and the availability of host poritid corals may be responsible for these heterogeneities. http://zoolstud.sinica.edu.tw/Joumals/47.1/17.pdf